1. Field of the Invention
This invention relates to a multi-spindle winder of a surface winding--center winding driving system according to which surface winding driving is primarily effected and center winding driving subsidiarily, the winder being provided with multi-spindle turrets having a plurality of winding spindles and being designed to produce continuously roll products consisting of a winding core with a given length of a transparent stretch film wound thereon.
2. Description of The Related Art
In winding up a transparent stretch film onto a winding core, it is required to wind the film under a constant tension throughout the entire process from the beginning to the end of winding so as not to entrap air among film layers of roll products and to obtain, from the viewpoint of good quality, so-called transparent rolls whose innermost core portions are seen through the film layers.
With a multi-spindle winder, operation is conducted so that an empty winding core is supported on a winding spindle provided on multi-spindle turrets at a first winding station; the leading end of a film fed from a delivery station is wrapped around the winding core while subsidiarily driving to rotate the winding spindle, concurrently with which a contact roller driven to rotate is put in contact with the surface of the film to initiate winding mainly by surface winding drive; at the time when most of a given length of the film is nearly fully wound, the multi-spindle turrets are turned a given angle, and simultaneously, the wound core shortly before full winding is transferred to a second winding station which is in a location receding from the first winding station relative to the delivery station and is wound up to a full-wound roll product at the second winding station; during which time a new empty winding core is supplied and ready for the next winding at the first winding station.
Here, it is critical that air be not entrapped among winding layers of the roll products not only under steady-state winding conditions at the stationary definite stations but also during turning motion of the turrets.
With a view to precluding air from being entrained among film layers being wound to form air layers in such manner as stated above, it is a known practice that the contact roller is brought into press contact with the winding contact line on roll products, thereby to intercept, at the inlet of the wound layers of the film, the air conveyed with the film being travelled.
When winding up is conducted at a stationary location, it is easy to effect a winding operation while putting the contact roller in contact with roll products, whereas during turning of the turrets, it is technically difficult to maintain the contact of only one contact roller while moving it to follow the winding station being shifted.
For this reason, a further second contact roller has hitherto been disposed in addition to a first contact roller and used for relay purpose. That is, during the former half turning period of the turrets, the first contact roller is moved in accordance with the movement of the winding station and then relayed to the second contact roller by bringing it into contact with roll products and releasing the first contact roller and subsequently, during the latter half period, the second contact roller is moved as the winding station is moved, whereby at least either of the contact rollers is always put in contact with roll products and the entrapment of air is precluded.
Thus, it is possible to prevent air from being entrapped by using a plurality of contact rollers for the purpose of relay, but nevertheless when notice is taken of tension imposed on the film during turning of the turrets, there are variable factors of the tension as enumerated below.
(A) The winding station gradually moves away from the delivery station with time.
(B) When the contact rollers move, following the movement of the winding station, they are affected by their revolution for following and turning motion as well as their spin rotation to cause the change in winding rotation number since the rotational drive system of them is usually composed of a planetary gear mechanism.
(C) The winding spindle supporting the winding core which is driven to rotate about its own axis is, during turning of the turrets, subject to change in rotation number by means of a planetary gear mechanism as a power transmission element for them.
(D) After the relay of the first contact roller to the second contact roller is finished, the first control roller moves and reverts to the initial first winding station. In the course of returning movement, the first contact roller serves also as a guide roller for guiding the film until the film is severed and hence the length in which the film develops stretching from the delivery station to roll products being wound, namely, the path length of the film is changed.
(E) The nip distances of the film (viz. distances between the nip point at the delivery station and the nip points of the first and second contact rollers) become longer with time during turning of the turrets. When the turrets are moved to the second winding station and stop, the nip distance there is considerably longer than that when winding is conducted at the first winding station.
The foregoing variable factors naturally affect the winding operation to vary the tension of the film. In a winder having such variable factors, it is extremely difficult to perform a winding operation while imparting constantly a definite tension and without air being entrapped among the winding layers. Particularly, in the case of a stretch film, irregularity of the film width and occurrence of local creases on the film are unavoidable and further, winding-up to a transparent roll product is not feasible.
To cope with these problems, attempts have been hitherto made to extremely slow down or stop the feed of film during turning motion of the turrets thereby to stock temporarily the film continuously payed out from the preceding step in an accumulator, but problems have been still encountered in that efficiency of production steps is diminished and creases, unevenness of width or other troubles, occur frequently in the roll products.
Further, by regarding the film portion of a roll product wound during turning of the turrets as a reject portion, after cutting process at the time of final winding-up, that portion only has been unwound and cut off. This method, however, entails occurrence of loss and further reduction in efficiency, and is not favorable.
Therefore, this invention has for a primary object to provide transparent rolls wound tightly by winding them under a constant tension consistently from the beginning to the end of winding operation while precluding the entrapment of air.
Another object of this invention is to perform winding even in the transitional period during turning of the turrets without diminishing winding speed and to permit sequence well synchronized and linked with the preceding step, thereby to maintain high efficiency of winding treatment.
A further object of this invention is to permit winding of a film stabilized in quality from the beginning to the end of winding and to attain enhancement in productivity and curtailment in cost without causing loss of the film.